A Senate panel looking at a bill on pollution and cancer heard today from environmental law activist Erin Brockovich.

Erin Brockovich’s work on a cancer cluster in the California desert town of Hinkley led to a lawsuit, and later a Hollywood movie.

Brockovich told the Environment and Public Works Committee that she’s hearing from people around the country about clusters of cancer victims. "According to the CDC in 2011," she said, "one in three people will develop cancer in his or her lifetime – one in three. As an advocate for the past 20 years, I have reached an undeniable conclusion: there are simply too many cancers in this country and not enough answers. And that is what these communities who reach out to me are trying to do – get answers to the most basic questions."

Brockovich said that one problem with tracking clusters is that people move. "And when people come down with cancer," she said, "they report it to the state in which they reside. They don’t report it to the state where they’re from, and so we could potentially be missing hundreds if not thousands of people, because we can’t track their movements and their geographic location."

Brockovich told the senators that she’s heard from high school classmates with cancer who reconnected on Facebook and found friends with the same cancer.

A bill cosponsored by California Democrat Barbara Boxer would require the EPA to investigate suspected disease clusters and create an online database.

A risk analyst warned about identifying random cancer cases as clusters – saying a mistake could close schools and ruin neighborhoods.